DTC P0455: EVAP Control System Large Leak Detected: Description

To determine if there is a leak or clog in the fuel system, PCM measures the change of the pressure in the fuel tank. The PCM turns on the evaporative emission ventilation solenoid to shut off the evaporative emission canister outlet port, then the evaporative emission purge solenoid is driven to set the fuel system into a negative pressure.

When the fuel system develops a vacuum of .29 psi (2 kPa), the purge solenoid is turned off and the fuel system vacuum is maintained at .29 psi (2 kPa). A change in vacuum pressure determines if a leak or clog in the fuel system exists. The test is stopped when fuel vapor pressure is judged to be too high.